MAX6664AEE+ Maxim Integrated Products, MAX6664AEE+ Datasheet - Page 14

• Manufacturer Part Number: MAX6664AEE+
• Description: IC TEMP MON FAN CNTRL 16-QSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX6664AEE+

• Function: Fan Control, Temp Monitor
• Topology: ADC, Multiplexer, Register Bank, Tachometer
• Sensor Type: External & Internal
• Sensing Temperature: -40°C ~ 125°C, External Sensor
• Output Type: I²C™/SMBus™
• Output Alarm: Yes
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Full Temp Accuracy: +/- 1 C
• Digital Output - Bus Interface: Serial (2-Wire)
• Digital Output - Number Of Bits: 11 bit
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

For the MAX6663, the alarm speed bit, bit 0 of status
register 1 (02h), indicates that the PWM duty cycle is
100%, excluding the case of fan spin-up. For the
MAX6653/MAX6664, this bit indicates that the THERM
output is low. Once this bit is set, the only way to clear it
is by reading status register 1. However, the bit does
not reassert on the next monitoring cycle if the condi-
tion still exists. It does assert if the condition is discon-
tinued and then returns.
At power-up, the MAX6653/MAX6663/MAX6664 are
monitoring temperature to protect the system against
thermal damage. The PWM outputs are in known states.
Note that although the "Monitoring" bit (Configuration
register 1, Bit 0) is enabled, automatic fan speed control
does not begin until a 1 is rewritten to Bit 0.
Other default conditions as listed in the Register Summary
section.
After applying power to the MAX6653/MAX6663/
MAX6664, set the desired operating characteristics (fan
configuration, alarm thresholds, etc.). Write to
Configuration register 1 last. When a 1 is first written to
Bit 0 of this register, fan control will commence as
determined by the register contents.
Follow these guidelines to reduce the measurement
error of the temperature sensors:
1) Place the MAX6653/MAX6663/MAX6664 as close
Table 15. Power-On Default Conditions
Temperature Monitors and
PWM Fan Controllers
14
Temperature Monitoring
PWM Output
PWM Mode
Duty cycle setting (not
enabled until a 1 is written
to Bit 0 of Register 00h)
PWM Polarity
as is practical to the remote diode. In noisy environ-
ments, such as a computer motherboard, this dis-
tance can be 4in to 8in (typ). This length can be
increased if the worst noise sources are avoided.
Noise sources include CRTs, clock generators,
______________________________________________________________________________________
Power-On Default Conditions
Monitoring at 4Hz
Low
PWM duty cycle control mode
33%
Inverted
(100% duty cycle = output high)
PC Board Layout
MAX6653
Alarm Speed
Monitoring at 4Hz
High
PWM duty cycle control mode
100%
Not Inverted
(100% duty cycle = output low)
2) Do not route the DXP-DXN lines next to the deflec-
3) Route the DXP and DXN traces in parallel and in
4) The 10-mil widths and spacing recommended in
5) Add a 200Ω resistor in series with VCC for best
Figure 6. Recommended DXP/DXN PC Traces
10 MILS
10 MILS
memory buses, and ISA/PCI buses.
tion coils of a CRT. Also, do not route the traces
across fast digital signals, which can easily intro-
duce 30°C error, even with good filtering.
close proximity to each other, away from any higher
voltage traces, such as 12VDC. Leakage currents
from PC board contamination must be dealt with
carefully since a 20MΩ leakage path from DXP to
ground causes about 1°C error. If high-voltage traces
are unavoidable, connect guard traces to GND on
either side of the DXP-DXN traces
Figure 6
only a minor improvement in leakage and noise over
narrow traces. Use wider traces when practical.
noise filtering (see Typical Operating Circuits).
MAX6663
are not absolutely necessary, as they offer
Monitoring at 4Hz
High
Automatic fan speed control mode
Automatic
Not Inverted
(100% duty cycle = output low)
GND
DXP
DXN
GND
MAX6664
(Figure
6).
10 MILS
MINIMUM
10 MILS